The present invention relates to a paper making method using a cationic neutral sizing agent.
More particularly, it relates to a method of improving a sizing effect of a cationic neutral sizing agent.
In the specification, the neutral sizing agent means a sizing agent which is used in acidic to neutral range (usually pH 4.5 to 8) in a paper making and can be used without a fixing agent. A cationic neutral sizing agent means the above defined neutral sizing agent having cationic component. A paper making method using a neutral sizing agent has been known. According to the conventional method, aluminum sulfate has not been used as a fixing agent whereby calcium carbonate can be used as a filler and a treatment of drainage has been easy. However, the neutral sizing agents have not been widely used because of disadvantages of unstable reproducibility of the sizing effect.
The inventors have studied on paper making methods using a cationic neutral sizing agent and have found that when a pulp slurry containing a sizing agent is treated with an oxidizing agent, the sizing effect has been remarkably improved and the stable sizing effect could be attained.